This invention relates to a system for monitoring and controlling the feed rate of a cut strip material which is adapted to be applied to a rotating cylindrical surface for use in the manufacture of fin tubing.
In particular, in order to appreciate fully the inventive advance of the present invention over the prior art systems, consideration is to be given to a number of related controls which are of interest. In this respect, reference is made to U.S. Pat. No. 3,808,789 to Hurley which discloses a system in which a plurality of strands is fed to a winding device from a plurality of supply packages or rolls, to feed rolls, and around a tension controlling means. After passing through the feed rolls, the strands enter a tension sensing device and pass through an opening to be wound onto a spool. The tension sensing device specifically includes a member having side and end rods over which the strands are fed. Increases and decreases in the tnesion of the strands causes movement of the mechanism which operates a potentiometer so as to control a magnetic clutch. The shaft moves against a biasing weight and against the action of a damping cylinder. Variations in resistance in the potentiometer changes the degree of slip in a magetic clutch which control the rotational speed of the drive rollers and thereby controls the rate of feed of the strands and consequently the tension exerted. However, it should be noted that this patent specifically points out that the rate of rotation of the motor and of its output shaft does not vary.
Another patent which is of interest is McCoy, U.S. Pat. No. 2,978,196 which is directed to a control means to control wire tension in a wire moving from one stage of a processing operation to a second stage of a processing operation, in particular, as the wire is advanced from a drawing die. The system of the patent includes both a stationary sheave and a movable sheave about which the wire is wrapped; a third sheave is provided connected to a movable arm which is associated with switches adapted to control a reversible motor. The patent discloses variation in the tension of the wire and provides for the aforesaid switches should the movements of the movable sheave be insufficient to control the tension of the wire. While the patent does disclose a movable sheave connected to an arm in order to control the tension in the wire, the patent specifically requires two movable sheaves and switches responsive to a spring biasing means which prevents constant movement of the arm, and points out that while there is a change in the tension of the wire, it is only gross changes for which compensation is effected.
Another patent which is pertinent to the present invention is U.S. Pat. No. 2,903,635 to Brooke et al. which discloses a feeler switch adapted to shut off a machine feeding roll should there be excessive slackness in the sheet being fed from the roll. This patent describes a "jockey roll" which moves between two different position to control slackness in the sheet. When the slackness is excessive, the arm moves to one position causing a cam to move the arm against a time delay switch. If the arm remains in this position for a sufficient period of time, the apparatus is shut off. There is no disclosure of a continuous variation in feed rate.
U.S. Pat. No. 3,613,975 to Knight also discloses a tension control system, and specifically an electronic control system for maintaining a predetermined tension in a material which is fed from a feed to a take-up station. Tension control is accomplished by means of a roller which moves within a guided pathway from a fixed position so as to activate a variety of electrical controls either to speed up or to slow down the feed rate as the roller moves from a constant datum plane.